To better evaluate potential uses for grape pomace (GP) waste, a comprehensive chemical composition analysis of GP in Virginia was conducted. Eight commercial white and red pomace samples (cv. Viognier, Vidal Blanc, Niagara, Petit Manseng, Petit Verdot, Merlot, Cabernet Franc, and Chambourcin) obtained from different wineries in Virginia, USA were used. For extractives, GPs contained 2.89%–4.66% titratable acids, 4.32%–6.60% ash, 4.62%–12.5% lipids with linoleic acid being the predominant (59.0%–70.9%) fatty acid, 10.4–64.8 g total phenolic content (gallic acid equivalents)/kg GP, 2.09–53.3 g glucose/kg GP, 3.79–52.9 g fructose/kg GP, and trace sucrose. As for non-extractives, GPs contained 25.2%–44.5% lignin, 8.04%–12.7% glucan, 4.42%–7.05% xylan, and trace amounts of galactan, arabinan, and mannan (less than 3% in total). Potential usages of these components were further examined to provide information on better valorization of GP. Considering the valuable extractives (e.g., polyphenols and oil) and non-extractives (e.g., lignin), designing a biorefinery process aiming at fully recover and/or utilize these components is of future significance.

Multiple analytical methods are used for quantification of total polyphenols and total flavanols in fruit juices and beverages. Four methods were evaluated in this study: Folin‐Ciocalteu (F‐C), Lowenthal permanganate (L‐P), 4‐dimethylaminocinnamaldehyde (DMAC), and the bovine serum albumin (BSA) precipitation method. Method validation parameters, including working range, limit of detection, limit of quantitation, precision (repeatability), accuracy, and specificity, were assessed and compared. The F‐C method was not specific to polyphenols, and the L‐P method had the widest working range but lacked accuracy. The DMAC method was the most specific to flavanols, and the BSA method was not suitable for quantification of smaller flavanols, such as catechin and epicatechin. Quantitative performance was evaluated using commercial fruit juice samples ( n = 14), apple juice samples of different cultivars ( n = 22), and commercial ciders ( n = 17). In general, the L‐P titration method and DMAC method resulted in higher quantitative values than the F‐C method and BSA precipitation method, respectively. However, ratios of results obtained by the L‐P and F‐C method ranged from 1 to 28, and ratios of results obtained by the DMAC and BSA precipitation method ranged from <1 to 280. This tremendous variation is likely due to variation in polyphenol composition and sample matrix. This information provides perspective for comparison of results obtained through these different methods, and a basis for choosing the most appropriate analytical method for quantification of polyphenols to address a specific research question when working with commercial fruit juice, apple juice from different apple cultivars, and commercial ciders. Practical Application: This study compared results obtained when four common polyphenol quantification methods were applied to a diverse selection of fruit juices and beverages with distinct polyphenol composition and sample matrix. The matrix and polyphenol composition of the samples significantly influenced the results. Our findings can help manufacturers of fruit‐based products choose the most appropriate analytical method for polyphenol quantification as part of a quality assurance program or to convey information on dietary polyphenol content to consumers. An assessment of analytical method validation parameters is provided for each of the four methods, which will help users of these methods to understand their limitations.

Amino acids and ammonium ions constitute the yeast assimilable nitrogen naturally present in apple juice, with free amino acids being the major constituent. Little information is available on the extent to which free amino acid composition in apple (Malus × domestica Borkh.) juice varies among juices used for fermentation. Twenty amino acids were quantified by UPLC‐PDA in juices from 13 apple cultivars grown in Virginia with potential use in cider making. The relative amino acid profile was significantly different among the apple juices evaluated. The total amino acid concentration ranged from 18 mg/L in Blacktwig juice to 57 mg/L in Enterprise juice. l‐Asparagine, l‐aspartic acid and l‐glutamine are the principal amino acids observed in most apple juices. Our results indicate that the relative concentration of amino acids in apples is different from that found in Vitis vinifera wine grapes, which are rich in l‐proline and l‐arginine. The impact of these differences on fermentation of apple juice by wine yeast strains warrants further research, as the amino acid composition of grape juice impacts wine quality both directly and indirectly via yeast metabolism. These results will inform future research on yeast metabolism and nitrogen management during cider fermentation. © 2018 The Authors Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling

Yeast assimilable nitrogen (YAN) is essential for yeast growth and metabolism during apple (Malus x domestica Borkh.) cider fermentation. YAN concentration and composition can impact cider fermentation kinetics and the formation of volatile aroma compounds by yeast. The YAN concentration and composition of apples grown in Virginia, USA over the course of two seasons was determined through analysis of both free amino nitrogen (FAN) and ammonium ion concentration. FAN was the largest fraction of YAN, with a mean value of 51 mg N L⁻¹ FAN compared to 9 mg N L⁻¹ ammonium. Observed YAN values ranged from nine to 249 mg N L⁻¹, with a mean value of 59 mg N L⁻¹. Ninety‐four percent of all samples analyzed in this study contained <140 mg N L⁻¹ YAN, a concentration generally considered the minimum level needed in grape‐based wines for yeast to fully utilize all of the fermentable sugars. FAN concentration was correlated with total YAN concentration, but ammonium concentration was not. Likewise, there was no correlation between FAN and ammonium concentration.